Perfluoropolymer, liquid composition, polymer electrolyte membrane, membrane electrode assembly and polymer electrolyte water electrolyzer

Abstract

To provide a perfluoropolymer capable of producing an electrolyte membrane excellent in mechanical strength in high temperature environments; as well as a liquid composition, polymer electrolyte membrane, membrane electrode assembly and polymer electrolyte water electrolyzer, obtainable by using the perfluoropolymer. The perfluoropolymer of the present invention contains perfluoromonomer units, does not substantially contain units having a halogen atom other than a fluorine atom, does not substantially contain units having a ring structure, and has acid-type sulfonic acid groups, wherein the perfluoromonomer units contain at least one type of units A selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units; the ion exchange capacity is from 0.9 to 1.4 milliequivalent/gram dry resin; and the storage modulus at 120° C. is at least 100 MPa.

What is claimed is: 
     
       1. A perfluoropolymer containing perfluoromonomer units, not substantially containing units having a halogen atom other than a fluorine atom, not substantially containing units having a ring structure, and having acid-type sulfonic acid groups, wherein:
 the perfluoromonomer units contain at least one type of units A selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units; 
 the ion exchange capacity is from 0.9 to 1.4 milliequivalent/gram dry resin; 
 the storage modulus at 120° C. is at least 100 MPa; and 
 the perfluoromonomer units further comprise tetrafluoroethylene units. 
 
     
     
       2. The perfluoropolymer according to  claim 1 , of which the hydrogen gas permeation coefficient under the conditions of a temperature of 80° C. and a relative humidity of 10% is at most 2.7×10 −9  cm 3 ·cm/(s·cm 2 ·cmHg). 
     
     
       3. The perfluoropolymer according to  claim 1 , which is a perfluoropolymer obtainable by converting precursor groups of a precursor polymer in which the acid-type sulfonic acid groups are in the form of the precursor groups, into the acid-type sulfonic acid groups, wherein the TQ value of the precursor polymer is at least 220° C. 
     
     
       4. The perfluoropolymer according to  claim 1 , wherein the content of units A is from 4 to 19 mol % to all units in the perfluoropolymer. 
     
     
       5. The perfluoropolymer according to  claim 1 , wherein the perfluoromonomer units comprise perfluoroallyl ether units represented by the formula (A-1): 
       
         
           
           
               
               
           
         
         where in the formula A-1, R F1  and R F2  are each independently a C 1-3  perfluoroalkylene group. 
       
     
     
       6. A liquid composition comprising the perfluoropolymer as defined in  claim 1  and a liquid medium. 
     
     
       7. A polymer electrolyte membrane comprising the perfluoropolymer as defined in  claim 1 . 
     
     
       8. The polymer electrolyte membrane according to  claim 7 , which further contains a reinforcing material. 
     
     
       9. A membrane electrode assembly comprising an anode having a catalyst layer containing a catalyst and a polymer having ion exchange groups, a cathode having a catalyst layer containing a catalyst and a polymer having ion exchange groups, and the polymer electrolyte membrane as defined in  claim 7 , disposed between the anode and the cathode. 
     
     
       10. The membrane electrode assembly according to  claim 9 , wherein at least one of the polymer having ion exchange groups contained in the anode and the polymer having ion exchange groups contained in the cathode, is a perfluoropolymer which is a perfluoropolymer containing perfluoromonomer units, not substantially containing units having halogen atoms other than fluorine atoms, not substantially containing units having a ring structure, and having acid-type sulfonic acid groups, wherein the perfluoromonomer units contain at least one type of units A selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units, the ion exchange capacity is from 0.9 to 1.4 milliequivalent/gram dry resin, and the storage modulus at 120° C. is at least 100 MPa. 
     
     
       11. A polymer electrolyte water electrolyzer comprising the membrane electrode assembly as defined in  claim 9 .